Why does the SCR not waste power as heat?

1. SCRs control how much of the AC sine wave is allowed to flow through the load. This is done by controlling the phase angle of conduction of either then SCR. This method controls how much of an AC sin wave is allowed to power the load. The effective amount of average power that a partial sine wave has is less than an average of a full sine wave. The result is that the load dissipates less heat because the effective average voltage is lower.